1. Field of the Invention
The present invention relates to an improved process or method for transferring at least one coating onto at least one geometrically defined surface of a lens substrate, which can be implemented in a short period of time without any risk of deformation of the lens substrate, which avoids the use of a liquid curable adhesive composition for adhesion of the coating to the lens substrate and results in the coating adhering to the lens substrate through an adhesive layer of uniform thickness.
2. Description of Related Art
It is a common practice in the art to coat at least one main surface of a lens substrate, such as an ophthalmic lens or lens blank, with several coatings for imparting to the finished lens additional or improved optical or mechanical properties. These coatings are designated in general as functional coatings.
Thus, it is usual practice to coat at least one main surface of a lens substrate, typically made of an organic glass material, with successively, starting from the surface of the lens substrate, an impact-resistant coating (impact resistant primer), an abrasion- and/or scratch-resistant coating (hard coat), an anti-reflection coating and, optionally, an anti-fouling top coat. Other coatings such as a polarized coating, a photochromic or a dyeing coating may also be applied onto one or both surfaces of the lens substrate.
Numerous processes and methods have been proposed for coating a surface of an ophthalmic lens and are disclosed.
U.S. Pat. No. 6,562,466 describes one process or method for transferring a coating from at least one mold part onto at least a geometrically defined surface of a lens blank comprising:                providing a lens blank having at least one geometrically defined surface;        providing a support or mold part having an internal surface bearing a coating and an external surface;        depositing on said geometrically defined surface of said lens blank or on said coating a pre-measured amount of a curable adhesive composition;        moving relatively to each other the lens blank and the support to either bring the coating into contact with curable adhesive composition or bring the curable adhesive composition into contact with the geometrically defined surface of the lens blank;        applying a sufficient pressure onto the external surface of the support so that the thickness of a final adhesive layer once the curable composition cured is less than 100 micrometers;        curing the layer of adhesive composition; and        withdrawing the support or mold part to recover the lens blank with the coating adhered onto the geometrically defined surface of said lens blank.        
U.S. Pat. No. 6,562,466 uses a liquid light or thermal curable adhesive composition to transfer the coating layers from the carrier to the surface of the lens substrate. The liquid curable adhesive composition is required to stick both to the exposed coating on the carrier and the geometrically defined surface of the lens substrate. The process requires to precisely dropping the liquid adhesive composition, either too much or too less of the liquid adhesive needs to be avoided, which renders the process more complicated and less cost effective. Furthermore, this process may cause optical distortions when the liquid adhesive composition is not spread out very evenly on the lens curved surface. In particular, when the liquid adhesive composition is spread using air pressure (inflatable membrane apparatus) applied on a flexible coating carrier, the applied pressure may not usually be uniform over the whole carrier surface, resulting in an uneven spreading of the liquid adhesive composition and a final cured adhesive layer having some variations in thickness.